From the data that Appleton and his colleagues were starting to amass, it was becoming clear that the ionospheric layers are produced by ultra-violet light emitted from the Sun. The regular behaviour of these layers was however disrupted during magnetic storms. Although the effects of magnetic storms have an effect at the mid latitudes of Slough, the effect is much more pronounced in the polar ionosphere. At the poles energetic charged particles cascade into the atmosphere after being guided there by the Earth's magnetic field. The resulting ionospheric data is therefore much more complex. In order to investigate this, staff from Ditton Park took some of their equipment to Tromso, Norway to make ionospheric measurements during the Second International Polar Year.